Ovulation refers to the time of your cycle that the egg is released from the ovum. This is the only time of the month you can become pregnant. Knowing when you ovulate can help you prevent or achieve pregnancy. Some women spot for a day or two in the middle of their menstrual cycle when they ovulate. For these women, this can be somewhat reliable in predicting ovulation. The spotting is much lighter than a period and is caused by the rapid plunge in estrogen that comes with the other hormonal changes immediately before ovulation. In other circumstances, this might be an inconvenience, but if you're trying to become pregnant, this can be an inexpensive indicator of the best time to have intercourse.